Temperature of pre-boil volume measurement

What temperature does beersmith assume the wort temperature is when calculating the pre-boil volume?  I know there is the cooling shrinkage adjustment for post boil in the equipment profile, but does that affect the preboil as well?  My wort is usually around 170 degrees F when I measure the pre-boil volume (with a stick that was calibrated at room temperature).  At that temperature, water takes up about 2.4% more space (volume) than it does at 70 degrees F (See https://www.engineeringtoolbox.com/water-specific-volume-weight-d_661.html ).  Should I be mentally adjusting the preboil volume for that 2.4% difference?  I realize with 5 gallon batches this is a very tiny difference, but once you get larger it starts to make a noticeable difference.  We are using beersmith with a 3bbl and 20bbl brewhouse, would like to get accurate efficiency numbers.

I have read both of these threads and neither give a definite answer.  It would be nice if beersmith had a user definable setting for what temperature the pre boil measurement was taken at.

http://www.beersmith.com/forum/index.php?topic=15099.0

http://www.beersmith.com/forum/index.php?topic=7249.0

If you look at the volumes tab, you can see the calculation of water volume.  BeerSmith starts with the volume target into the fermenter.  It then adds on the loss to chiller and trub to that volume.  To that total, it calculates the end of boil volume by adding on the amount of thermal expansion.  From that point on, all the volumes are at that expanded temperature, including the initial infusion volume.

You are correct that the expansion coefficient at 170 F is around 2.4%, BeerSmith does not scale the volume by temperature though.  It applies the whole expansion coefficient which is in the equipment profile. 

From experience and several years of playing with the software, I can tell you that you can get the system to balance out properly using this single expansion coefficient, but it is misleading when you start trying to brew on multiple systems,such as I do from time to time.

I used to have my expansion coefficient set to 2% to account for my post-mash/pre-boil volume measurement which I normally take in the low 150's.  When I do BIAB mashes, I would need to start by adjusting the starting water volume since I measure it out at/around room temperature the night before I brew.  Since BeerSmith does not have a spot for recording post-boil volume, it just did not make sense to me to apply the expansion coefficient at boiling (4%).  I use a spreadsheet for tracking my process variables to update my equipment profiles and in that sheet my volumes are automatically adjusted for the temperature so that I can track gravity points more accurately.

So I guess for now the best way to account for the volume difference is to subtract 1.6% (Assuming the beersmith pre-boil number is based on the 4% expansion, 4%-2.4%=1.6%) from the estimated pre-boil volume that beersmith gives, and then adjust the boil-off value until the estimated pre-boil volume matches the number calculated from the 1.6% subtraction.  Keeping in mind that the pre-boil value that beersmith will display is incorrect after that.

Sure would be nice to be able to configure that temperature manually...

Edit: or uncheck the automatic boil vol calculation and manually enter the pre-boil volume (the incorrect number based on 4%), and then still adjust the boil off number until the post boil number is correct?

Actually, you can set the thermal expansion to any amount you want.  Mine used to be at 2% to account for the temperature that I usually take my volume readings after I remove the bag and grains from the kettle.  This worked really well to balance out my system and understand my natural variability. For me it was easier to get the pre-boil volume correct and follow the volumes throughout the process in order to dial in the software to my system.  I knew that if I hit that volume and the expected gravity that everything else would fall into place at the end of the process.


Now that I am comfortable with my process and how it works in BeerSmith, I have set my expansion down to 0% so that I don't need to do any recalculation of starting water.  The gravity points still follow for a volume corrected to room temp balance and I know where my mash efficiency will fall to within 1%.